A search for SiO maser emission from symbiotic Miras.

A sample of 29 dusty symbiotics, mostly containing Mira primaries, has been observed in the 86GHz, v=1, J=2-1 transition of SiO, to look for maser emission. Apart from R Aqr, a known maser source, no objects were detected. By comparing our results with those previously obtained on normal Miras and LPVs, we find that in symbiotics the masers are generally underluminous, or absent. By considering the possible influence of the UV radiation and tidal effects of the compact companion on the maser sites, we conclude that the likely reason for the lack of SiO maser emission from symbiotics whose orbits are not too wide is tidal disruption of the stationary or deeper layers in the Mira atmosphere. For probable wide orbit systems like RX Pup the mechanism inhibiting the SiO maser emission is still unknown. We present and discuss a time series of maser spectra of R Aqr.